Integrated multi-mode mammography/tomosynthesis x-ray system and method

ABSTRACT

A system for multi-mode breast x-ray imaging which comprises a compression arm assembly for compressing and immobilizing a breast for x-ray imaging, an x-ray tube assembly, and an x-ray image receptor is provided. The system is configured for a plurality of imaging protocols and modes.

This application claims the benefit of U.S. provisional application Ser.No. 60/631,296, filed Nov. 26, 2004 and entitled “INTEGRATED MULTI-MODEMAMMOGRAPHY/TOMOSYNTHESIS X-RAY SYSTEM AND METHOD”, the entire contentsof which are incorporated herein by reference.

FIELD

This patent specification pertains to x-ray mammography and, morespecifically, to an integrated system for selectively carrying out x-raymammography and/or tomosynthesis imaging and a method of using such asystem.

BACKGROUND

X-ray mammography has long been a screening modality for breast cancerand other lesions, and also has been relied on for diagnostic and otherpurposes. For many years, the breast image was recorded on x-ray filmbut more recently digital x-ray image receptors have come into use, asin the Selenia™ mammography system available from Hologic Inc. ofBedford, Mass. and its division Lorad Corporation of Danbury, Conn. Formammograms, a cone-shaped or pyramid-shaped x-ray beam passes throughthe compressed breast and forms a two-dimensional projection image. Anyone of a number of orientations can be used, such as cranial-caudal (CC)or MLO (mediolateral-oblique) orientation. More recently, breast x-raytomosynthesis has been proposed. The technology typically involvestaking two-dimensional (2D) projection images of the immobilized breastat each of a number of angles of the x-ray beam relative to the breastand processing the resulting x-ray measurements to reconstruct images ofbreast slices that typically are in planes transverse to the x-ray beamaxis, such as parallel to the image plane of a mammogram of the samebreast. The range of angles is substantially less than in computerizedtomography, i.e. substantially less than 180°, e.g. ±15°. Tomosynthesistechnology is described in U.S. patent application Ser. No. 10/723,486filed Nov. 26, 2003; a prototype of a unit with at least some of thedescribed features was shown at the 2003 Radiological Society of NorthAmerica meeting in Chicago, Ill. Additional prototypes are in clinicaltesting in this country as of the filing of this patent specification.Other approaches to tomosynthesis also have been proposed: see, e.g.,U.S. Pat. Nos. 4,496,557, 5,051,904, 5,359,637, 6,289,235, and6,647,092, published U.S. Patent Applications Nos. 2001/0038861,2004/066882, 2004/0066884, and 2004/0066904, and Digital ClinicalReports, Tomosynthesis (GE Brochure 98-5493, November 1998). How toreconstruct tomosynthesis images is discussed in DG Grant,“Tomosynthesis: a three-dimensional imaging technique”, IEEE Trans.Biomed. Engineering, Vol BME-19, #1, (January 1972), pp 20-28. See,also, U.S. Provisional Application Ser. No. 60/628,516, filed Nov. 15,2004, and entitled “Matching geometry generation and display ofmammograms and tomosynthesis images”. Mammography systems can also beused in interventional procedures, such as biopsy, by adding a biopsystation (for example, the StereoLoc II™ Upright Stereotactic BreastBiopsy System, which is available from Hologic, Inc.). The patents,applications, brochures, and article cited above are hereby incorporatedby reference in this patent specification as though fully set forthherein.

In clinical use, it can be desirable for a number of reasons to assessboth tomosynthesis images and conventional mammograms of the patient'sbreasts. For example, the decades of conventional mammograms haveenabled medical professionals to develop valuable interpretationexpertise. Mammograms may offer good visualization ofmicrocalcifications, and can offer higher spatial resolution comparedwith tomosynthesis. Tomosynthesis images may have different desirablecharacteristics—e.g., they may offer better visualization of structuresthat can be obscured by overlying or underlying tissue in a conventionalmammogram.

While the existing and proposed systems for x-ray mammography andtomosynthesis offer many advantages, it is believed that a need stillexists for further improvements to make mammography/tomosynthesis moreuseful, and that it is particularly desirable to make it possible to usethe same system in different modes of operation and thereby reduceacquisition and operating costs and provide greater clinical value andconvenience.

SUMMARY

This patent specification describes examples of systems and methods formulti-mode breast x-ray imaging. A single system carries out breastimaging in modes that include standard mammography, diagnosticmammography, dynamic imaging such as with a contrast agent and atdifferent x-ray energies, tomosynthesis imaging, combined standard andtomosynthesis imaging during a single breast compression, needlelocalization, and stereotactic imaging with a biopsy station mounted tothe system.

In an example of a system using the teachings of this patentspecification, a compression arm assembly for compressing andimmobilizing the breast for x-ray imaging, an x-ray tube assembly, andan x-ray image receptor can be angled relative to each other fordifferent imaging protocols and modes. They can be independently rotatedand synchronized as needed, or can be mechanically linked forappropriate synchronized rotation. A patient shield can be mounted tothe compression arm assembly to provide a mechanical interlock againstpatient contact with the rotating x-ray tube assembly. A fullyretractable anti-scatter grid can be used that can cover the imagingarea of the x-ray receptor in some modes but be retracted completelyoutside the imaging area for other modes.

The exemplary system further includes a breast compression paddle thatis laterally movable, under manual control or when motorized andoperating under software control. The compression paddle can shiftautomatically depending on the view to be acquired. For example, thepaddle can be centered on the x-ray receptor for a CC view, shifted toone lateral side of the receptor for an MLO view of one breast and tothe other lateral side of the receptor for an MLO view of the otherbreast. The paddle can be automatically recognized by the system whenmounted so that the shifts can be adjusted to the type of paddle.

The compression paddle can be easily removable from a support that has amechanism for laterally moving the paddle and for allowing the paddle totilt for better conformance with the breast for selected image modes butlocking the paddle against tilt for other modes. With the movementmechanism in the support and not integral with the paddle, the paddlecan be simple and inexpensive, and easy to mount to and remove from thesupport. A number of relatively inexpensive paddles of different sizesand shapes can be provided and conveniently interchanged to suitdifferent procedures and patients.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a gantry and an acquisition workstationin accordance with an example of the disclosed system.

FIG. 2 is an enlarged view of a portion of the system of FIG. 1, with atube arm assembly in a rotated position.

FIG. 3 is a front elevation of the apparatus of FIG. 2.

FIG. 4 is a side view of a gantry with a biopsy station and a spacer,with schematic illustration of other mechanisms.

FIG. 5 is an enlarged view of a portion of FIG. 1.

FIG. 6 is a block diagram of the disclosed system when connected toother systems.

FIG. 7 is a flow chart illustrating a general work flow for thedisclosed system.

FIG. 8 is a flow chart illustrating one of several examples of work flowfor a standard mammography mode.

FIG. 9 is a flow chart illustrating one of several examples of work flowfor an image detector subsystem in the standard mammography mode.

FIG. 10 is a perspective view of the structure of FIG. 4.

FIG. 11 is similar to FIG. 2 but shows a tube arm assembly angleddifferently.

FIG. 12 is a front elevation of the structure of FIG. 11.

FIG. 13 is a flow chart illustrating one of several examples of workflow for a tomosynthesis mode.

FIG. 14 is a flow chart illustrating one of several examples of workflow for an image detector subsystem in the tomosynthesis mode.

FIG. 15 is a flow chart illustrating one of several examples of workflow for a combination mode.

FIG. 16 is a flow chart illustrating one of several examples of workflow for an image detector subsystem in the combination mode.

FIG. 17 is an enlarged side view of a structure for removably mounting abreast compression paddle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In describing examples and preferred embodiments illustrated in thedrawings, specific terminology is employed for the sake of clarity.However, the disclosure of this patent specification is not intended tobe limited to the specific terminology so selected and it is to beunderstood that each specific element includes all technical equivalentsthat operate in a similar manner.

FIGS. 1-6 illustrate a non-limiting example of a multi-mode mammography/Tomosynthesis system comprising a gantry 100 and a data acquisitionwork-station 102. Gantry 100 includes a housing 104 supporting a tubearm assembly 106 rotatably mounted thereon to pivot about a horizontalaxis 402 (FIG. 4) and carrying an x-ray tube assembly 108. X-ray tubeassembly 108 includes (1) an x-ray tube generating x-ray energy in aselected range, such as 20-50 kV, at mAs such as in the range 3-400 mAs,with focal spots such as a nominal size 0.3 mm large spot and nominalsize 0.1 mm small spot (2) supports for multiple filters such asmolybdenum, rhodium, aluminum, copper, and tin filters, and (3) anadjustable collimation assembly selectively collimating the x-ray beamfrom the focal spot in a range such as from 7×8 cm to 24×29 whenmeasured at the image plane of an x-ray image receptor included in thesystem, at a maximum source-image distance such as 75 cm. Also mountedon housing 104, for rotation about the same axis 402, is a compressionarm assembly 110 that comprises a compression plate 122 and a receptorhousing 114 having an upper surface 116 serving as a breast plate andenclosing a detector subsystem system 117 comprising a flat panel x-rayreceptor 502 (FIG. 5), a retractable anti-scatter grid 504 and amechanism 506 for driving and retracting anti-scatter grid 504. Housing104 also encloses the following components schematically illustrated inFIG. 4: a vertical travel assembly 404 for moving tube arm assembly 106and compression arm assembly 110 up and down to accommodate a particularpatient or imaging position, a tube arm assembly rotation mechanism 406to rotate tube arm assembly 106 about axis 402 for different imagingpositions, a detector subsystem rotation mechanism 408 for rotatingcomponents of detector subsystem 117 (such as x-ray receptor 502) aboutaxis 402 to accommodate different operation modes, and couple/uncouplemechanism 410 to selectively couple or uncouple tube arm assembly 106and compression arm assembly 110 to and from each other, and tube armassembly 106 and detector subsystem 117 to and from each other. Housing104 also encloses suitable motors and electrical and mechanicalcomponents and connections to implement the functions discussed here. Apatient shield 200, schematically illustrated in FIG. 2, can be securedto compression arm assembly 110 to provide a mechanical interlockagainst patient contact with the rotating x-ray tube arm assembly 106.Work-station 102 comprises components similar to those in the Selenia™mammography system, including a display screen (typically a flat paneldisplay that may include touch-screen functionality), user interfacedevices such as a keyboard, possibly a touch-screen, and a mouse ortrackball, and various switches and indicator lights and/or displays.Work-station 102 also includes computer facilities similar to those ofthe Selenia™ system (but adapted through hardware, firmware and softwaredifferences) for controlling gantry 100 and for processing, storing anddisplaying data received from gantry 100. A power generation facilityfor x-ray tube assembly 108 may be included in housing 104 or inwork-station 102. A power source 118 powers work-station 102. Gantry 100and work-station 102 exchange data and controls over a schematicallyillustrated connection 120.

As illustrated in FIG. 6, additional storage facilities 602 can beconnected to work-station 102, such as one or more optical disc drivesfor storing information such as images and/or for providing informationto work-station 102 such as previously obtained images and software, ora local printer (not shown). In addition, the disclosed system can beconnected to a hospital or local area or other network 604, and throughthe network to other systems such as a soft copy workstation 606, a CAD(Computer Aided Detection) station 608 for computer-processingmammography and/or tomosynthesis images to identify likelyabnormalities, an image printer 610 for printing images, a technologistworkstation 612, other imaging systems 614 such as other mammographysystems or systems for other modalities for exchange of images and/orother information, and to a PACS (Picture Archiving) systems 616 forarchiving images and other information and/or retrieving images andother information.

The illustrated system has several modes of operation. An example oftypical workflow generally applicable for each mode is illustrated inFIG. 7, and several examples of operational modes are discussed below.Of course, this is only one example and workflow steps may be arrangeddifferently. In all modes, the operator can perform x-ray exposure usingmanual setting of technic factors such as mA and mSec, or can use anautomatic exposure control as known in the art to set the exposure time,kV and filter modes for an image, for example by using a short,low-x-ray dose pre-exposure. Work-station 102 is set up to record theexposure technic information and associate it with the breast image forlater review. breast image for later review. The steps illustrated inFIG. 7 are:

701, in which a user/technologist logs in;

702, in which patient demographics are entered;

703, which comprises review of previous examination;

704, in which the study is selected;

705, in which the technique is set up or an auto-setup of technique isperformed;

706, in which the patient is positioned;

707, in which the technique is verified and/or modified;

708, in which the technique is confirmed;

710, in which the exposure button is pushed;

710, in which the technologist reviews the preview image, such as forparameters indicated in the box to the right;

711, in which a decision is made whether to accept the image;

712, in which the image is rejected if step 711 has not accepted theimage;

713, in which the image accepted in step 712 is saved (sent to theoutput device);

714, in which a test is made whether after step 714 (or 713) the studyis complete and, if not, the process returns to step 705; and

715, which closes the procedure if step 715 determines that the study iscomplete.

In standard mammography mode, typically used for screening mammography,tube arm assembly 106 and compression arm assembly 110 are coupled andlocked together by 410 in a relative position such as seen in FIG. 1,such that an x-ray beam from x-ray tube assembly 108 illuminates x-rayreceptor 502 when the patient's breast is compressed by compressiondevice 112. In this mode, the system operates in a manner similar tosaid Selenia™ system to take a mammogram. Vertical travel assembly 404and tube arm rotation mechanism 406 can make vertical adjustments toaccommodate a patient, and can rotate tube arm assembly 106 andcompression arm assembly 110 together as a unit about axis 402 fordifferent image orientations such as for CC and for MLO images. Forexample, tube arm assembly 106 and compression arm assembly 110 canrotate between (−195°) and (+150°) about axis 402. As in the Selenia™system, compression device 112 includes a compression paddle 122 thatcan move laterally, in a direction along the chest wall of a patient, toadjust for different imaging orientations. However, as described furtherbelow, the mechanism for supporting and moving compression paddle 122 isdifferent. Typically, anti-scatter grid 504 is over x-ray receptor 502in the standard mammography mode to reduce the effect of x-ray scatter.FIG. 8 illustrates a typical workflow for an exposure in standardmammography mode, and FIG. 9 illustrates an example of the operation ofdetector subsystem 117 in standard mammography. Of course, these areonly examples; other workflow steps or orders of steps can be usedinstead. The steps illustrated in FIG. 8 are:

801, in which the examination is setup and the patient is positioned;

802, in which the expose button is pressed;

803, in which the system is ready for exposure and x-ray begins;

804, in which exposure takes place in an x-ray window;

805, in which a decision is made whether to view a preview image;

806, in which the preview image is viewed if the decision at step 805was to do so;

807, in which a test is made to determine whether the study is complete,and the process is directed to repeating step 801 is the study is notcomplete;

808, in which a full image is captured, whether or not previewed; and

809, in which the procedure is closed if the test at step 807 determinesthat the study is complete; and

810, in which the captured image is saved;

The steps illustrated in FIG. 9 are:

901, in which the detector receives an image capture request;

902, in which the detector is ready for image capture;

903, in which an exposure window is open;

903, in which the detector is read out;

904, in which the image data is available to the host; and

906, in which a test is made whether the host is done with reading thedata and, if the host is done reading the data, returns theprocess tostep 901 but if the host is not done with reading the data, recyclesthrough step 906 until the test answer is that the host is done readingthe data.

In a diagnostic mode, the patient's breast can be spaced from uppersurface 116, for example by an x-ray translucent spacer 1002 (FIG. 10),with the system otherwise similar to FIG. 1, for a magnification of upto 1.8, for example. In this mode, as in standard mammography, tube armassembly 106 and compression arm assembly 110 are locked to each otherand can move up or down and rotate about axis 402 for different imageorientation. A different spacer 1002 can be used for a different degreeof magnification. Also, differently shaped or dimensioned compressionpaddles 122 can be used for different breast compression effects. Thex-ray tube in x-ray tube assembly 108 can be set to a smaller focal spotsize to improve a diagnostic image. In this mode, anti-scatter grid 504typically is retracted when magnification is used such that grid 504 iscompletely out of the image. The user can elect not to use a spacer 1002in diagnostic imaging, in which case anti-scatter grid 504 can be usedover the entire image.

In a dynamic imaging mode, a number of breast images are taken while thepatient's breast remains compressed. In one technique, an agent such asiodine is injected into the patient and after a suitable waiting timesuch as about one minute for a maximum uptake, two images breast aretaken in rapid succession, for example one at an x-ray energy just abovethe K-edge of iodine and one at an energy just below the K-edge.Alternatively, a succession of breast images can be taken at a singlex-ray energy band or bands just above and below the K-edge, or atanother x-ray energy range, to track the uptake of agent over time.Another technique adds taking a baseline breast image before or soonafter injecting the agent and using it together with later breast imagesto generate subtraction images that provide better visualization ofanatomy that may be of interest. Still another dynamic imaging modetechnique comprises injecting a contrast agent and taking a successionof images over a period such as 5-7 minutes, for example one image everyminute, and processing the image data to generate for each pixel, or atleast for each pixel of interest, a histogram of the change in the pixelvalue, to thereby use the manner in which pixel values change todifferential abnormal tissue. For this mode, work-station 102 can storepreset data that commands gantry 100 and work-station 102 to take adesired sequence of images for the dynamic mode technique selected bythe operator, such that the command data sets the appropriate parameterssuch as x-ray energy, dose, timing of images, etc. Alternatively, suchprocessing to assess changes in pixel values can be done for a region ofinterest rather than over individual pixels, to produce information suchas a measure of changes in the average pixel values in the region ofinterest.

In tomosynthesis mode, tube arm assembly 106 and compression armassembly 110 are decoupled by unit 410 such that compression armassembly 110 stays in one position, compressing the patient's breast,while tube arm assembly 106 rotates about axis 402, for example betweenthe position illustrated in FIG. 2 to that illustrated in FIG. 11, or±15° relative to compression arm assembly 110. Tomosynthesis can becarried out for different image orientations, so that compression armassembly 110 can be rotated about axis 402 (alone or together withassembly 106) for a desired image orientation and locked in place, andthen tube arm assembly 106 can be rotated relative to that position ofcompression arm assembly 110 for tomosynthesis imaging over ±15° or someother desired angular range. In one example, 11 images are taken duringan angular sweep of tube arm assembly 106, one every approximately 3°.However, a different number of images can be taken, for example up to 21during a single sweep. For tomosynthesis images, the x-ray tube in x-raytube assembly 108 continuously rotates and the x-ray tube is pulsed foreach image, for example, for x-ray energy pulses each lastingapproximately 100 mSec, although pulses of different duration can beselected. Alternatively, the rotational motion can stop for taking eachimage, or continuous motion without pulsing can be used (and the timingof data measurements relied to define pixel values). As seen in FIGS. 2,3, 5, 11 and 12, in this mode mechanism 506 fully retracts anti-scattergrid 504 away from x-ray receptor 502 so grid 504 is out of the image.Also as seen in these Figs., while the breast remains immobilized incompression arm assembly 110 during the angular sweep of tube armassembly 106, x-ray receptor 502 rocks within receptor housing 114. Inthis rocking motion, controlled by unit 408 (FIG. 4), a line normal tothe image face of x-ray receptor 502 may keep pointing to the focal spotof the x-ray tube in x-ray tube assembly 108. Alternatively, therotation of tube arm assembly 108 and rocking of x-ray receptor 502 canbe through different angles; for example, tube arm assembly 108 canrotate through 15° while x-ray receptor 502 rocks through 5°, i.e. therocking angle can be an amount one-third that of assembly 108.Synchronous rotation of tube arm assembly 106 and rocking of x-rayreceptor 502 can be achieved by controlling separate motors for each or,alternatively, through using a motor to drive tube arm assembly 108 anda mechanical coupling between the rotation of tube arm assembly 106 androcking of x-ray receptor 502. Image data can be obtained and processedinto tomosynthesis images for display and/or storage as described in thematerial incorporated by reference, for example in co-pending patentapplication Ser. No. 10/723,486 or in U.S Provisional Application No.60/628,516, filed Nov. 15, 2004. FIG. 13 illustrates a typical workflowfor tomosynthesis mode operation, and FIG. 14 illustrates an example ofthe operation of detector subsystem 117 in that mode. Again, these areonly examples, and other steps or orders of steps can be used instead.

The steps illustrated in FIG. 13 are:

1301, in which the examination is setup and the patient is positioned;

1302, in which the expose button is pressed;

1303, in which the system is ready for exposure and x-ray begins;

1304, in which exposure takes place in an x-ray window, and is repeatedas indicated in the box to the right;

1305, in which a test is made whether to view a projection preview image

1306, in which the preview image is viewed if the decision at step 1306was to do So;

1307, in which a test is made to determine whether the study iscomplete, and the process is directed to repeating step 1301 is thestudy is not complete;

1308, in which reconstruction and full image capture take place, whetheror not the preview image was viewed in step 1307;

1309, in which the procedure is closed if the test at step 1307determines that the study is complete; and

1310, in which the image from step 1308.

The steps illustrated in FIG. 14 are:

1401, in which the detector receives a tomo capture request;

1402, in which the detector is ready for capture;

1403, in which an exposure window is open;

1404, in which the detector is read out;

1404, in which the expose/readout cycle is repeated the expose/readoutcycle is repeated as indicated in the box to the right; and

1405, in which all image frames are available to the host; and

1406, in which a test is made whether the host is done with reading thedata and, if so, the process is returned to step 1401 but if not, step1407 recycles until the test answer is that the host is done reading thedata.

In a combination mode, during a single compression of the patient'sbreast the system takes a conventional mammogram and tomosynthesisimages. In this mode, while the breast remains compressed in compressionarm assembly 110, (1) tube arm assembly 106 sweeps and x-ray receptor502 rocks, each through an appropriate angle, and exposures are takenfor tomosynthesis images, and (2) a standard mammogram is taken. Thestandard mammogram can be taken at a 0° relative angle between tube armassembly 106 and a normal to the imaging plane of x-ray receptor 502,and can be taken before or after the tomosynthesis images are taken orbetween the taking of two successive tomosynthesis images. Typically,each tomosynthesis image utilizes substantially lower x-ray dose thanthe standard mammogram. For example, the total x-ray dosage fortomosynthesis imaging in one sweep of tube arm assembly 106 can beapproximately the same as that for a single standard mammogram, or up toapproximately three times that dosage. The relationship between the twodosages can be user-selected. FIG. 15 illustrates an example of workflowfor the combination mode, and FIG. 16 illustrates an example of theoperation of detector subsystem 117 in that mode. The steps illustratedin FIG. 15 are:

1501, in which the examination is setup and the patient is positioned;

1502, in which the expose button is pressed;

1503, in which the system is ready for exposure and the scan starts;

1504, in which tomo exposure takes place in an x-ray window andprojection exposures are repeated as indicated in the box to the right;

1505, in which a test is made whether to view a projection preview image

1506, in which the preview image is viewed if the decision at step 1506was to do so;

1507, in which the C-arm is auto-positioned for standard scan, whetheror not step

1505 determined that a preview image should be viewed;

1508, in which reconstruction is performed;

1509, in which a standard exposure is performed (x-ray begins);

1510, in which image preview takes place (tomo and standard);

1511, in which a test is made to determine whether the study iscomplete, and the process is directed to repeating step 1501 is thestudy is not complete;

1512, in which complete reconstruction and image capture take place; and

1513, in which the procedure is closed if the test at step 1511determines that the study is complete.

The steps illustrated in FIG. 16 are:

1601, in which the detector receives a combo capture request;

1602, in which a tomosynthesis image cycle is performed;

1603, in which a standard image cycle is performed; and

1604, in which a test is made to determine if the host is done withreading data and, if so, the process is returned to step 1601 but ifnot, the process cycles through step 1604 until the test shows that thehost is done with reading data. Again, these are examples, and differentsteps or orders of steps can be used instead. For example, a preferredapproach may be to take the standard mammogram first, then move arm 106to one end of its rotational range for tomosynthesis and take thetomosynthesis images. The order in which the two types of images aretaken may be optimized such that the overall imaging time is minimized,and an order that achieves such minimization can be the preferred order.The exposure (tube current mA, tube voltage kVp, and exposure lengthmsec) techniques for the standard mammogram and the tomosynthesisexposures can be set manually, or by using automatic methods. If thestandard mammogram is taken first, its exposure techniques can be usedto set an optimal technique for the subsequent tomosynthesis images, andvice versa. The exposure technique can be modified dynamically, if thesoftware senses that the signal reaching the image receptor is eithertoo low or too high and adjust subsequent exposures as needed.

In a stereotactic mode, during a single compression of the patient'sbreast at least two images are taken, for example one at (+15)° angleand one at (−15°) angle of tube arm assembly 106 relative to compressionarm assembly 110, although other angles can be used and more images canbe taken. X-ray receptor 502 can remain in place for this procedure, orcan be rocked through a selected angle, for example through an anglesufficient to maintain the same orientation of the imaging surface ofreceptor 502 relative to tube arm assembly 106. A spacer 1002 can beused for magnification. If x-ray receptor 502 remains in place despiterotation of arm 106, or if spacer 1002 is used, anti-scatter grid 504 isfully retracted; if x-ray receptor 502 maintains its orientationrelative to tube arm assembly 106 and no spacer 1002 is used,anti-scatter grid 504 need not be retracted. As is known in the art, thetwo or more images can be used to identify the location of a lesion, sothat needle biopsy can be used, for example with an upright needlebiopsy station 412 (FIG. 4) in a manner similar to that used with thecommercially available Selenia™ system and StereoLoc II™. A compressionpaddle 122 appropriate for needle biopsy typically is used when takingthe stereotactic images. Alternatively, some or all of the images takenin the tomosynthesis mode and/or in the combined mode can be used toidentify the location of a lesion for biopsy, in which case acompression paddle 122 appropriate for the purpose typically is usedwhen taking the images.

In needle localization mode, x-ray images can be taken after a biopsy orother needle is inserted into the compressed breast. For this purpose,imaging such as in the stereotactic mode, the tomosynthesis mode, or thecombined mode can be used.

In the disclosed system, compression paddle 122 is movable laterally, asgenerally described in U.S. Patent Application Publication No.2005/0063509 A1, hereby incorporated by reference herein. In addition,compression paddle 122 can pivot about an axis along the patient's chestwall to conform the breast shape in certain procedures, as discussed insaid U.S. Pat. No. 5,706,327. However, in the system of this patentspecification compression paddle 122 is mounted differently and moves ina different manner.

As illustrated in FIGS. 5 and 17, compression paddle 122 is removablymounted to a support 510 that moves up and down compression arm assembly110 as needed for breast compression. To mount compression paddle 122onto 510, a projection compression paddle 122 a of the paddle engages aprojection 510 a of the support, and a projection 122 b of the paddlelatches onto projection 510 b of the support. Projection 510 a isspring-loaded, such as by a spring schematically illustrated at 510 c toallow for pivoting compression paddle 122 about an axis where it latchesonto 510, as illustrated by arrow A, for better conformance with thecompressed breast in some imaging protocols. Other imaging protocols mayrequire compression paddle 122 not to pivot, in which case projection510 a is locked in place by a locking mechanism in 510 (not shown) tokeep compression paddle 122 in place relative to support 510. Thelocking mechanism can be manually set to a lock position, and manuallyunlocked by the operator. Alternatively, the locking mechanism can becontrolled through an operator input at gantry 100 or work-station 102.A sensing mechanism can be included to sense whether compression paddle122 is locked against pivoting, to provide information that work-station102 can use for setting imaging protocols such as for automated breastcompression and automated exposure methods. Two knobs 510 d, one on eachlateral side of support 510, can be manually rotated to move projection510 b and thus compression paddle 122 laterally such that it compress abreast that is not centered laterally on upper surface 116, for examplefor MLO imaging. Each knob 510 d can operate a mechanism such as anendless screw rotating in a nut secured to projection 510 b.Alternatively, or in addition, projection 510 b and thus compressionpaddle 122 can be driven laterally by a motor, under control of operatorswitches or other interface at gantry 100 or at work-station 102, orautomatically positioned laterally under computer control.

Importantly, compression paddle 122 is driven for lateral movement bycomponents that are a part of support 510. Thus, compression paddle 122can be a simple structure, and can even be disposable, with a new oneused for each patient or for only a few patients. This can simplify andreduce the cost of using the system, because an imaging facility usuallystocks a number of different paddles for different purposes. If thelateral movement mechanism is integral with a compression paddle, thepaddle assembly is considerably larger, heavier and more expensive. Butwith a compression paddle 122 that relies for lateral movement onsupport 510, and is easily mounted by hand and without tools to support510, by sliding compression paddle 122 a into projection 510 a andlatching projection paddle 122 b onto projection 510 b, and is easilyremoved by reversing the process, the expense of keeping a number ofdifferent compression paddles in stock or replacing paddles with newones is greatly reduced, as are the time and convenience when changingfrom one type of compression paddle to another. Compression paddle 122can include a bar code that is automatically read by a bar code readerin support 510, to keep work-station 102 informed of the paddlecurrently mounted to support 510, for use in automating imagingprotocols. For example, the bar code information can be checked toensure through computer processing that the type of paddle that iscurrently mounted on support 510 matches the imaging that will becommanded, and the information from the sensor for whether compressionpaddle 122 is locked in non-tilting mode can be used to automaticallymake adjustments for compression height to ensure accurate automaticx-ray exposure operation. Further, the bar code information identifyingthe paddle can be used to automatically set collimation in x-ray tubeassembly 108 so that the x-ray beam matches the size and shape of thecurrently installed compression paddle 122.

The above specific examples and embodiments are illustrative, and manyvariations can be introduced on these examples and embodiments withoutdeparting from the spirit of the disclosure or from the scope of theappended claims. For example, elements and/or features of differentillustrative embodiments may be combined with each other and/orsubstituted for each other within the scope of this disclosure andappended claims.

1. A system for multi-mode breast x-ray imaging, comprising: an x-rayimage receptor; an x-ray tube assembly selectively emitting an x-raybeam directed toward the x-ray image receptor; and a breast immobilizerbetween the x-ray tube assembly and the x-ray image receptor, whereinsaid x-ray tube assembly and said x-ray image receptor are supported andconfigured for movement according to a plurality of imaging protocolsand modes, including a protocol and mode in which the x-ray tubeassembly moves along a curved path through one angle relative to thebreast immobilizer and the x-ray image receptor concurrently movesthrough a different angle, in angular extent, relative to the breastimmobilizer.
 2. The system of claim 1, wherein said x-ray tube assemblyand said x-ray image receptor are mechanically linked for movement as aunit for at least one of the plurality of imaging protocols and modes.3. The system of claim 1, wherein said x-ray tube assembly and saidx-ray image receptor move relative to each other for at least one of theplurality of imaging protocols and modes.
 4. The system of claim 1,including a compression arm assembly supporting said breast immobilizerand said x-ray image receptor, wherein said compression arm assembly andsaid x-ray tube assembly are locked to each other for at least one ofthe plurality of imaging protocols and modes.
 5. The system of claim 1,including a compression arm assembly supporting said breast immobilizerand said x-ray image receptor, wherein said compression arm assembly andsaid x-ray tube assembly move independent of each other for at least oneof the plurality of imaging protocols and modes.
 6. The system of claim1, including a compression arm assembly supporting said breastimmobilizer and said x-ray image receptor, wherein said compression armassembly, said x-ray tube assembly and said x-ray image receptor aremechanically linked for movement as a unit for at least one of theplurality of imaging protocols and modes.
 7. The system of claim 1,including a compression arm assembly supporting said breast immobilizerand said x-ray image receptor, wherein said compression arm assembly,said x-ray tube assembly and said x-ray image receptor move independentof each other for at least one of the plurality of imaging protocols andmodes.
 8. The system of claim 1, wherein said modes include at least amammography mode and a tomosynthesis mode.
 9. The system of claim 1,wherein said modes include a combination mode for taking both amammogram and tomosynthesis images during a single breast compression.10. A tomosynthesis/mammography system comprising: an x-ray source, abreast immobilizer, and an x-ray imaging receptor; said source, receptorand breast immobilizer being supported selectively for operation in: (a)a mammography mode in which the source, receptor and breast immobilizerrotate as a unit, and (b) a tomosynthesis mode in which the sourcerotates relative to the breast immobilizer and the receptor rocksrelative to the breast immobilizer; and wherein in the tomosynthesismode the angle through which the source rotates is different in angularextent from the angle through which the receptor rocks.
 11. An x-raytomosynthesis /mammography system as in claim 10 including a receptorhousing shrouding at least a portion of said receptor and having anupper surface between the receptor and the source, said receptor beingfixed relative to said upper housing in said mammography mode butrocking relative to the receptor housing in said tomosynthesis mode. 12.An x-ray tomosynthesis /mammography system as in claim 10 including afirst support arm supporting the source and a second support armsupporting the receptor, and a main support to which said first andsecond arms are mounted for rotation as a unit in the mammography modebut for rotation of at least one relative to the other in thetomosynthesis mode.
 13. An x-ray tomosynthesis /mammography system as inclaim 12 in which said first and second arms rotate about a common axis.14. An x-ray tomosynthesis /mammography system as in claim 12 includinga couple/uncouple mechanism for locking the first and second arms forrotation as a unit in the mammography mode and uncoupling the first andsecond arm for rotation of at least one relative to the other in thetomosynthesis mode.
 15. An x-ray tomosynthesis /mammography system as inclaim 10 including an anti-scatter grid occupying a first positionbetween the source and the receptor for system operation in themammography mode and a grid drive moving the grid away from the firstposition thereof for system operation in the tomosynthesis mode.
 16. Anx-ray tomosynthesis /mammography system as in claim 15 in which saidgrid drive is motorized.
 17. An x-ray tomosynthesis /mammography systemas in claim 10 including a compression paddle mounted for tiltingrelative to the receptor in selected imaging modes but locked againsttilting in other imaging modes.
 18. An x-ray tomosynthesis /mammographysystem as in claim 10 including a compression paddle mounted formovement toward and away from the receptor to compress a patient'sbreast and for lateral movement relative to the receptor.
 19. An x-raytomosynthesis /mammography system as in claim 18 including a mechanismautomatically shifting the compression paddle laterally relative to thereceptor depending on a view to be acquired.
 20. An x-raytomography/mammography system as in claim 10 including a paddle supportmounted for movement toward and away from the receptor, and acompression paddle removably mounted to the paddle support for movementtherewith toward and away from the receptor housing and for lateralmovement relative to the paddle support.
 21. An x-raytomography/mammography system as in claim 18 in which said lateralmovement of the compression paddle relative to the paddle support ismotorized.
 22. A breast tomosynthesis system as in claim 11 in whichsaid receptor housing encloses the x-ray imaging receptor.
 23. A breasttomosynthesis method comprising: selectively locking to each other afirst support arm supporting a source of an x-ray beam and a second armsupporting an x-ray imaging receptor for rotation as a unit andunlocking the first and second arm from each other for individualrotation of at least one of the arms relative to the other; selectivelyrocking the imaging receptor relative to the second support arm whilerotating the first support arm; acquiring projection x-ray image datafrom the receptor while rotating the source support arm and rocking theimage receptor; and computer-processing the image data into images fordisplay and selectively displaying at least some of the images; in whichthe acquiring step comprises selectively acquiring tomosynthesis x-rayprojection image data while the receptor is rocking and mammographyx-ray image data when the receptor is not rocking.
 24. A breasttomosynthesis method as in claim 23 including storing an imagingprotocol in a computerized work station coupled with said source andreceptor, said work station automatically controlling the acquiring stepand the computer-processing step according to said stored imagingprotocol to selectively acquire said tomosynthesis and mammography imagedata.
 25. A breast tomosynthesis method as in claim 24 including ananti-scatter grid automatically controlled by said work stationaccording to said stored protocol to move between a postion in the pathof said x-ray beam and a position outside said path.
 26. A breasttomosynthesis system as in claim 24 including a compression paddleautomatically controlled by said work station according to said protocolto move to positions laterally offset relative to the receptor.